8. A car travels at a constant velocity of 70 mph for one hour. By the end of the second hour, the car's velocity was 60 mph. At the end of the third hour, the car's velocity was 80 mph. During which hour was their acceleration positive? During which hour was their acceleration negative?

Question

Physics

Demetrius Ho

16 January, 20:28

8. A car travels at a constant velocity of 70 mph for one hour. By the end of the second hour, the car's velocity was 60 mph. At the end of the third hour, the car's velocity was 80 mph. During which hour was their acceleration positive? During which hour was their acceleration negative?

+2

Answers (1)

Know the Answer?

Kallie Hicks · Answer 1

Positive acceleration is in third hour and negative acceleration is in second hour.

Explanation:

Velocity of car in first hour = 70 mph

Velocity of car in second hour = 60 mph

Velocity of car in third hour = 80 mph

Acceleration = Change in velocity / Time

Acceleration in second hour = (60 - 70) / 1 = - 10 mph²

Acceleration in third hour = (80 - 60) / 1 = 20 mph²

So positive acceleration is in third hour and negative acceleration is in second hour.